1. Dynamic Modeling for Relativistic Heavy Ion Collisions
Huichao Song
Peking University
CPOD2014, Bielefeld, Germany, Nov.17-Nov.21, 2014
11/20/2014

2. QGP-the most perfect fluid in the world?
BNL News, 2005
How perfect is the QGP fluid?

3. What is viscosity Assume: (RHIC&LHC)
Shear viscosity – measures the resistance to flow
act against the buildup of flow anisotropy
Bulk viscosity – measures the resistance to expansion
act against the buildup of
radial flow
Heat conductivity – measures the ability of heat transfer
Assume: (RHIC&LHC)

4. Hydrodynamics & its Hybrid Model

5. Viscous Hydrodynamics
Evolution equations for shear pressure tensor and bulk pressure
Assume zero net baryon density & heat conductivity at RHIC and the LHC
Song & Heinz PLB08, PRC08
2+1-d: OSU, INT, Stony Brook, Pudue, Calcutta (2008), Crakow, Frankfurt(2010) … …
3+1-d: Mcgill(2011), MSU(2012), Crakow(2012), Nagoya(2013)… …

6. Viscous Hydro + Hadron Cascade Hybrid Model
QGP
HRG
Initial conditions viscous hydro hadron cascade
viscous hydro (QGP)
+ URQMD (HRG)
viscous hydro (QGP & HRG)
ideal hydro (QGP & HRG)
H. Song, S. Bass, U. Heinz, PRC2011

7. Event-by-event hydrodynamics
Single shot simulations: smoothed initial conditions (before 2010)
E-b-E simulations: fluctuating initial conditions (since 2010)
B. Schenke et al, Phys.Rev. C85, (2012)

8. Extracting QGP viscosity from elliptic flow data – VISHNU results

9. VISHNU hybrid model & QGP viscosity
H. Song,et.al, PRL2011
MC-KLN
MC-Glauber
-Main uncertainties come from initial conditions
-Other uncertainties (much smaller)
-Initial flow, bulk viscosity, single shot vs. e-b-e calculations
(each of them shift V2 by a few percent, partial cancellation among them)

10. V2 at RHIC and LHC
Song, Bass & Heinz, PRC 2011
The average QGP viscosity is roughly the same at RHIC and LHC

11. LHC: spectra for identified hadrons
Song, Bass & Heinz,PRC 2014
-a nice fit of spectra for pions, kaons and proton

12. Spectra of Strange & Multi-strange Hadrons
X.R. Zhu, H. Song et al., in preparation
-a nice fit of spectra for Lambda, Xi, and Omega

13. for pions, kaons & protons at LHC
VISHNU
Song, Bass & Heinz,PRC 2014
A very nice fit of V2(PT) for all centrality bins at LHC from VISHNU hybrid model

14. v2 of Strange & Multi-strange Hadrons
X.R. Zhu, H. Song et al., in preparation
-Nice descriptions of Lambda, Xi and Omega V2 at various centralities

15. Initial State Fluctuations, Final State Correlations
& the QGP viscosity

16. Uncertainties from Initial Conditions
H. Song, S. Bass, U. Heinz, T. Hirano, and C. Shen, PRL2011
MC-KLN
MC-Glauber
Main uncertainties come from initial conditions
MC-KLN, larger HIGHER value of QGP viscosity
MC-Glauber, smaller LOWER value of QGP viscosity

17. MC-KLN & MC-Glauber initializations & V3
Pure viscous hydro simulations :
Qiu, Shen & Heinz, PLB2012
V3 prefer lower value of QGP viscosity

18. Initialization & Pre-equilibrium: Updates after 2011
-fluctuations of nucleon positions:
MC-Glauber, MC-KLN
-fluctuations of color charges (in the framework of CGC):
IP-Glasma: B. Schenke et al., arXiv: ; [nucl-th]
Correlated Fluctuation: B. Muller & A. Schafer, arXiv: [hep-ph] .
-fluctuations of local gluon numbers (in the famework of MC-KLN):
Multiplicity fluctuations: A. Dumitru and Y. Nara, Phys. Rev. C 85, (2012)
-Pre-equilibriums:
URQMD initialization: H.Petersen & M. Bleicher, Phys. Rev. C81, ,2010
AMPT initialization: L. Pang, Q.Wang & X.Wang, arXiv: [nucl-th]
EPOS/NEXUS initialization: K. Werner et al., Phys. Rev. C83:044915,2011
… … … …
Mostly, the effects of initializations /pre-equilibrium dynamics was studied with ideal hydro. Their quantitative influences on are still unknown.

19. Flow at RHIC & LHC: results from IP-Glasma + MUSIC
Gale, Jeon ,Schenke, Tribedy &Venugopalan PRL2013

20. New Observables for Higher Order Flow Harmonics
Luzum & Ollitrault,
Qiu & Heinz,12-08
C. Gale et al.
12-09
-They are all sensitive to the QGP viscosity
will constrain initialization models, tightening the limit on
-A further study of flow data in different aspects, using e-b-e hybrid model

21. Massive Data evaluation
Exp Observables
Theoretical Inputs:
particle yields
spectra
- elliptic flow
- triangular flow & higher order
flow harmonics
- event by event Vn distributions
higher-order event plane
correlations
… … …
- type of initial conditions
initial flow
- starting time
EoS
shear viscosity
- bulk viscosity
- relaxation times
- freeze-out/switching cond.
… … … …

22. Massive data evaluation
Early CHIMERA Results
(Comprehensive Heavy Ion Model Evaluation and Reporting Algorithm)
Spectra
spectra
elliptic flow
HBT
R. Soltz, et al., PRC2013
Please also refer to the work from MSU-DUKE collaboration, arXiv:

23. Massive data evaluation
Bernhard & Bass, JET collaboration

24. Bulk Viscosity Long , but not full lists of articles:
J.Noronha-Hostler, J.Noronha and F.Grassi, arXiv: [nucl-th]
M. Habich and P. Romatschke,  arXiv: [hep-ph].
J.Noronha-Hostler, et.al.,  Phys.Rev. C 88, (2013)
K.Dusling and T.Schäfer,   Phys.Rev.C 85, (2012)
P. Bozek,  Phys. Rev. C81, (2010)
H.Song and U.WHeinz,   Phys. Rev. C81, (2010)
G.Torrieri et al. Phys.Rev. C78, (2008).
K. Rajagopal et al. JHEP 1003, 018(2008) .
A. Monnai et al. Phys.Rev. C (2009)
R.Fries et al. Phys.Rev. C (2008) .
… … … … … …

25. The interplay between shear and bulk viscosity
Visc. suppression
of elliptic flow
shear visc.
shear+ bulk visc.
ideal
Song & Heinz PRC09
QGP
HRG
Min. AdS/CFT
prediction
-Bulk viscous effects are much smaller than shear ones due to the critical slowing down near phase transition (Song & Heinz PRC09)
-One can extract the QGP shear viscosity from exp data without large contamination from bulk viscosity
Introduction 25

26. Ultracentral Collisions: bulk visc. & NN correlations
Shen, Qiu and Heinz 2013
G. Denicol, QM2014
-MC-Glauber & MC-KLN: can not simultaneously fit V2 and V3
-IP+Glasma + NN correlations + bulk viscosity nicely reproduces Vn in
ultra-central collisions

27. Soft Particle Yields, Chemical & thermal Freeze-out at the LHC
J. Stachel,SQM 2013
Tch = 165MeV
Tch = 150MeV
v.s.

28. dN/dy for identified hadrons (RHIC & LHC)
Song, Bass & Heinz,PRC 2014
RHIC : 200 A GeV Au+Au
LHC : 2.76 A TeV Pb+Pb
-VISHNU nicely describes the multiplicity for pions, kaons & protons
-B-Bbar annihilations plays an important role for a nice fit of the proton data
VISHNU : Tsw= 165MeV
Please also refer to F. Becattini et al., PRC2012

29. dN/dy for identified hadrons (LHC)
X.R. Zhu, H. Song et al., in preparation
-VISHNU nicely describes the multiplicity for various hadrons at the LHC

30. dN/dy for identified hadrons (LHC)
X.R. Zhu, H. Song et al., in preparation
VISHNU
most central collisions

31. Statistical Model vs. VISHNU
Statistical Model : Tch ~ 150 MeV
VISHNU : Tsw= 165MeV
- Statistical Model: Tch is extracted from final hadron yields; averaged chemical freeze-out temperature for final stable hadrons
- VISHNU: Tsw corresponds QGP chemical freeze-out; different hadrons may have different chemical freeze-out temperature.

32. Chemical freeze-out for various hadrons in UrQMD
X.R. Zhu, H. Song et al., in preparation

33. Thermal freeze-out for various hadrons in UrQMD
X.R. Zhu, H. Song et al., in preparation
-earlier freeze-out for Xi and Omega!

34. phi-meson

35. Elliptic flow for phi at the LHC
Song, Bass & Heinz, PRC 2014
200A GeV
Au+Au
-Hadron cascade: small cross sections for phi
-mass ordering between phi and proton are independent of collision energies, centralities & theoretical details
T. Hirano
3+1-d ideal hydro+JAM

36. Elliptic flow for phi at the LHC
Song, Bass & Heinz, PRC 2014
ALICE 2014

37. Elliptic flow for phi at the LHC
Song, Bass & Heinz, PRC 2014
STAR Preliminary
ALICE 2014

38. phi V2 in strong & weakly coupling limit
Song, Bass & Heinz, PRC 2014
-hydro + Tdec =165 MeV weakly coupling limit
-hydro + Tdec =100 MeV strong coupling limit
-VISHNU: small cross sections for phi

39. phi V2 in strong & weakly coupling limit
Song, Bass & Heinz, PRC 2014
-hydro + Tdec =165 MeV
weakly coupling limit
-hydro + Tdec =100 MeV
strong coupling limit
VISHNU:
small cross sections for phi
STAR Preliminary
ALICE 2014

40. Summary

41. Summary -Extraction from elliptic flow data using VISHNU indicates:
(MC-Glauber; MC-KLN)
-Slightly larger averaged QGP viscosity at the LHC
-Recent developments on initialization models: color charge fluctuations;
multiplicity fluctuations; initial flow fluctuations … …
-To implement e-b-e simulations to further study other flow will help us to constrain initialization models, tightening the limit on
-New flow data: triangular flow & higher order flow harmonics, higher-order event plane correlations e-b-e vn … ...
-massive data evaluation are needed
-VISHNU could nicely describe the yields of various hadrons
-B-Bbar annihilations is important to describe the proton yields at the LHC
VISHNU: an indication of different chemical freeze-out temperature for various hadrons